i have an '89 volvo 740 w/turbo and a 2.3ltr. it was driving and running fine today. I parked it and went into the store when i came out to start it the car reved up to 3500rpm's and it will not lower. I have checked for vaccuum leaks and found none. The dealership says it's electrical. Is there anyone out there that can tell me exactly what's wrong so I can fix it?